Carburetor



Nov. 29, 1938.

R. F. .BRACKE CARBURETOR Filed March 22, 1935 2 Sheets-Sheet 1 laI,

NOV. 29, R F BRACKE CARBURETOR Filed March 22, 1935 2 Sheets-Sheet 2ysa-md Nov. 29, 193e UNITED STATES PATENT ori-ICE csmsumrrort Robert F.Bracke, chicago, n1. Application Maren zz, 1935, serial No. 12,463

s claims. (o1. zen- 34) My invention pertains tov carburetors and ismore particularly concerned with carburetors of the fuel-lift type.

An object of my invention is to provide a carburetor which will affordmore rapid acceleration for the internal combustion engine to which itis attached.

Another object is to provide an improved carburetor of this type whichis simple and economical to manufacture and which is durable andtrouble-free in service.

Other objects and advantages will become apparent as the descriptionproceeds.

In the drawings,

Figure l is a vertical elevation, partly in section, showing acarburetor embodying my invention;

Figure 2 is a vertical section through the carburetor of Figure l, beingtaken on the line 2-2 of Figure 1; and

Figure 3 is a fragmentary cross-sectional view taken on the line 3-"3 ofFigure 2.

My improved carburetor is illustrated as comprising an upper casting Aand a lower casting B secured together by bolts Il) and having anairtight gasket I2 confined between adjacent portions of the twocastings.

'I'he casting A includes an air horn I4 having its upper end4 of reducedexternal diameter to facilitate the attachment of any usual form of aircleaner and silencer where the use of such a device is deemed desirableor necessary.

Part of the air entering the air horn I4 passes into the nozzle Venturitube I6 where it mixes with fuel supplied through diagonal ducts I8communicating with the throat of the nozzle I6. Annular space 20 andpassageway 22 connect the ducts I8 with a fuel chamber 24 whichconstitutes a source of fuel supply for the nozzle I6.

'I'he lower end of the nozzle I6 is surrounded by the upper end 26 of anair valve 28 which controls the admission of secondary air from the airhorn I4 into the mixing chamber 38. A spring 32 urges the air valve 28toward closing position. The nozzle I6 discharges against the flat uppersurface of an inverted cup-shaped portion 34 provided by the air valve28, and this flat surface causes the primary mixture delivered by thenozzle I8 to flowradially outward where it mixes with secondary airadmitted past the air valve 28.

I'he upper portion of the air valve which surrounds the lower end of thenozzle I6 is preferably provided with heat insulating packing 36. Theinverted cup-shaped portion 34 of the air valve, together with the airvalve guide 88, Hforms a closed chamber 89 into which suction may'beintroduced for opening the air valve against the l tension of its spring82.

'I'he chamber 39 communicates withthe upper 5 l end of throttle bore 40by means of passage 4I l .and the small orifice 43 provided by the plug45A g press-fitted into one end of the passage 4I. By this means thesuction existing in the upper part of throttle bore 48 is communicatedto the cham- 10 ber v39, and the valve 28 is opened an amountproportional tothe degree of suction obtaining in the upper end ofthrottle bore 48. v

The combustible mixture flows `from the mixing chamber 30 into thethrottle bore 48 which 15 is provided with the usual throttle valve 42carried by a shaft 44 pivotally mounted in the lower f casting B.' Oneend of theshaft 44 has an arm 46 adapted to be connected to the usualaccelerator pedal of an automobile, and a second arm 20 48 adapted to beconnected to the usual hand throttle of the automobile. The arm 46can'ie the usual adjustable stop 50.

Part of the air entering the air horn I4 passes through a lateralopening 52 at one side of the 25 air-horn and flows downwardly through aconduit 54 into a chamber 56 provided by a sheet-metal cup 58 secured inplace by a star-shaped spring plate 60 and screw 62. A booster Venturitube 64 has its inlet end in communication with the 30 chamber 56. Thisbooster discharges into a duct 86 communicating with throttle bore 48through an orifice 68 in which there is a tapered pin 'I8 having anenlarged upper head confined between a plate 12 and the adjacent portionof the air 35 valve 28 so that the pin 'l0 reciprocates with the airvalve.

The throat of the booster 64 is provided with radial ducts communicatingwith a passage 82 connecting'with the top of the fuel chamber 24. 40'I'he function of this booster 64 is to draw fuel into the fuel chamber24 through pipe 84 which connects with the main fuel tank of theautomobile usually located at the rear of the vehicle and below thecarburetor. 'I'he fuel chamber v24 45 is provided with the usual inletvalve 86 controlled by the float 88.

A choke plate'14 is located between the metal cup 58 and the adjacentportion of the casting B. This choke plate has an L-shaped opening 'I650 which maintains communication at all times' between the chamber 56and the conduit 54. 'Ihis choke plate has a second opening 18 whichcontrols'the inlet to the booster Venturi tube 64. In the normalposition of the choke plate, there is 55 free communication between theinlet to the booster 64 and the chamber Il, but when the choke plate ismoved to full or part choke position, the inlet to the booster 'I8 iscorrespond.- ingly reduced so that the suction created in the fuelchamber 24 by the booster 34 varies with the position of the choke plate14.

When the choke plate 'I4 is in substantially the full choke position,the end 88 of the L-shaped slot 13 establishes communication between thechamber i8 and a duct 82 leading to the chamberV 39 formed beneath thesecondary air valve 28 so that under full choke conditions atmosphericair is admitted beneath the air valve 28. The duct 92 admits air to thechamber 38 faster than the air in the chamber can be withdrawn throughthe small oriilce 43, and the-result is that the air valve 28 remainsclosed and an extremely rich mixture is supplied to the engine.

The choke plate 'I4 has a stop 84 which rests against a pin 96 when thechoke plate is in the position it assumes when the engine is operatingnormally. 'I'he choke plate 14 has an arm 98 adapted for connection tothe usual choke control mechanism for moving the choke plate to anydesired position. When the choke plate is in the full choke position,the arm 88 rests ,against A that the full power of the engine willimmediately become available for accelerating purposes. To insure fullopening of the secondary air valve at such times, I provide a source ofvacuum which is connected to the chamber 33 beneath the secondary airvalve whenever rapid engine accelera: tion is desired.

At one side of the mixing chamber 33 I provide a vacuum chamber Illhaving its lower end in communication with a cylinder |82 connected to apart of the throttle bore 4l beneath the throttle valve 42 by means of aduct |84. The upperend of vacuum chamber |88 is provided with a valveseat |06 and valve |88 controlling communication between thischamber'and a passageway Il. leading to the chamber 38 beneath thesecondary air valve 28.

A piston ||2 is located in the cylinder |32 and has a piston rod I I4.'I'he valve |83 is mounted on the upper end of the piston rod ||4. Aspring lli is confined between the valve seat |83 and a washer |I8supported on a shoulder suitably provided by the piston rod II4.

In the normal operation of the engine, the piston ||2 and valve |03assume the position shown in Figure 2 of the drawings. The piston ||2does not make a perfect seal with its cylinder |32 so that air isexhausted from the chamber |88 by the suction existing in thethrottlebore 43 beneath the throttle valve 42 until the degree of vacuumobtaining in the chamber |38 is substantially equal to that existing onthe engine side of the throttle valve 42.

When the throttle valve is quickly opened to obtain rapid engineacceleration, the pressure in the throttle bore 4I| rises to almostatmospheric pressure, and this is communicated to the underside of thepiston 2. Because of the relatively high vacuum existing in the chamber|00, the substantially atmospheric pressure acting on the under sideof-the piston ||2 moves this piston upwardly against the tension ofspring IIS and -This immediately produces complete or substantiallycomplete opening of the air valve 28, thus permitting the maximum now ofsecondary air therepast and supplying the engine cylinders with themaximum amounts of combustible mixture. 'I'he piston ||2 fitssufficiently tightly in its cylinder |82 to greatly restrict the leakageof air into the chamber |03 past the piston ||2, so that the eii'ect ofthe vacuum chamber Ill on the secondary air valve is not immediatelydissipated but continues over an appreciable period of time.

. Because of the rise in pressure in the throttle bore 43 during periodsof acceleration, the booster becomes ineffective during suchaccelerating periods to draw fuel from the main'fuel tank into the fuelchamber 24. `This fuel chamber 24 therefore mu'st be madek largeenoughto supply all oi' the fuel needed by the engine during periods ofacceleration without replenishment from the main fuel tank during suchacceleratingperiods.

The carburetor is further provided with a fuel pump |23 comprising acylinder |22 extending downwardly into the fuel chamber 24, and a piston|24 located in the cylinder |22 and operated by a piston rod |28. 'Ihelower end of piston rod |23.rests on one end of an Aadjustable stop |23provided by one of the two arms of a lever |38 which is pivoted on thecasting B at |32 and which has its second arm adapted for engagement bya cam I 34 rotatable with the throttle valve shaft 44.

'I'he piston |24 is moved downwardly by a spring |36 confined betweenthe upper side of the piston and an opposing part of the casting A. Thepiston is provided with ports |38 which are practically closed duringthe pumping movement of this piston by a valve disk I 40. 'Ihe valvedisk |48 has a small orifice to provide the necessary fuel for engineidling, and when the engine is operating at greater' than idling speed,the disk |43 is drawn upwardly away from the ports |38 to permit thepassage of additional fuel to the engine.

Ihe upper end of cylinder |22 communicates with passage 22 through anorifice |42 in which there is located a metering pin |44 attached to andreciprocable with the piston |24.

Leakage of air into the fuel chamber 24 around the piston rod |23 isprevented by4 a duct |48 which connects an intermediate portion of theguide for this piston rod with the portion of the throttle bore 48 whichis beneath the throttle valve 42.

The operation of my improved carburetor is as follows:

Part of the air entering the horn I4 passes through the nozzle IC whereit mixes with fuel drawn from the fuel chamber 24 and delivers thismixture against the inverted cup-shaped portion 34 of the air valve 28.'I'his mixture then flows radially and mixes with any secondary airflowing past the air valve 28. From the mixing chamber 33 the resultingcombustible mixture flows to throttle bore 4II and past throttle valve42 to the engine cylinders.

When the engine is operating at part or full throttle, the suctionexisting in the upper part of throttle bore 4II draws air from chamber38 through orifice 43 and passage 4|, and the resultant suction createdin this chamber 39 moves secondary air valve 28 downwardly a distanceproportional to the suction existing in the upper part of throttle bore40. At the same time pin is moved downwardly and restricts the dischargefrom booster 64 to a greater extent so that the booster 64 alwaysmaintains substantially the same degree of vacuum in the fuel chamber24. Under normal operating conditions, this vacuum -is suiiicent to drawfuel from the main fuel tank when the float 88 drops sufficiently topermit the inlet valve 86 to open.

When the throttle valve 42 is quickly opened to provide rapid engineacceleration, the suction chamber I00 is placed in communication withthe chamber 39 beneath the secondary air valve by the resulting upwardmovement of the piston I I2 and valve |08. This results in drawing thesecondary air valve 28 downwardly to admit the maximum volume ofsecondary air, whereupon the engine cylinders receive a maximum chargeof combustible mixture and the engine produces its maximum torque. Thequick opening of the throttle valve 42 actuates the accelerator pump|20, whereupon additional fuel is supplied to the nozzle I6 whichdelivers an exceptionally rich mixture best suited for rapidacceleration.

During the accelerating period, the booster 64 becomes ineiective tosupply fuel, and the fuel maintained at all times in the fuel chamber 24suiices to carry the engine through the accelerating period, at thetermination of which the booster 64 again functions to rell the fuelchamber 24. During this accelerating period, however, the booster 64still exerts a regulating or calibrating influence on the nozzle I6,thereby insuring that the latter supplies the propermixture foracceleration.

When the choke is applied, the chamber 38 beneath the air valve isconnected with atmosphere through duct 92 and end 90 of opening 16 inchoke plate 14, with the result that the spring 32 holds the secondaryair valve in closed position. At the same time the available air supplyfor the booster 64 is materially decreased so that the booster creates anegligible vacuum in the fuel chamber 24. This permits the nozzle I6 tosupply a richer mixture to the engine, thereby facilitating startingwhen the engine is cold.

The carburetor disclosed and claimed herein is an improvement over thatdisclosed and claimed in my prior application, Serial No. 6,421, ledFebruary 14, 1935.

While I have disclosed and claimed only one embodiment of my invention,it is to be understood that my invention may assume numerous forms andthat the scope of my invention is limited solely by the followingclaims.

I claim:

l. In a carburetor of the class described, the combination of a nozzlefor supplying a mixture of fuel and air, a mixing chamber into whichsaid nozzle discharges, a valve for admitting air directly to saidmixing chamber, a vacuum chamber, means for creating a vacuum therein,and means for utilizing the vacuum in said chamber to open said valve,said means becoming effective only when the carburetor is conditionedfor rapid engine acceleration.

2. In a carburetor of the class described, the combination of a fuelsupply nozzle, a mixing chamber into which said nozzle discharges, asuction actuated valve for admitting secondary air to said chamber, asuction chamber beneath said valve, a spring for closing said valve, athrottle bore communicating with said mixing chamber, a restrictedconduit connectingsaid throttle bore with said suction chamber wherebysaid valve is opened an amount proportional to the degree of suctionexisting in the upper part of said bore, a vacuumchamber, a conduitconnecting said vacuum chamber with said suction chamber, a valvenormally closing said conduit, means for opening said last-namedvalve'when the carburetor is conditioned for rapid engine acceleration,and an accelerator pump for simultaneously supplying said nozzle with anadditional quantity of fuel.

3. In a carburetor of the class described, the combination of afuel-feeding nozzle, a mixing chamber into which said nozzle discharges,a throttle bore communicating with said mixing chamber, a throttle valvelocated in said bore, an air valve for admitting secondary air to saidmixing chamber, a spring for closing said valve, suction-operated meansfor opening said valve, a restricted conduit connecting said last-namedmeans with said throttle bore on the inlet side of saidA throttle valve,a vacuum chamber, a conduit connecting said chamber with saidsuctionoperated means, a valve in said conduit, a passage connectingsaid vacuum chamber with a part of .the throttle bore on the engine sideof said throttle valve, a restriction for limiting ow through saidconduit, and a piston for opening said last-mentioned valve when rapidengine acceleration is desired.

4. In a carburetor of the class described, the combination of afuel-feeding nozzle, a mixing chamber into which said nozzle discharges,a throttle bore communicating with said mixing chamber, a throttle valvelocated in said bore, an air valve for admitting secondary air to saidmixing chamber, a spring for closing said valve, suction-operated meansfor opening said valve, a restricted conduit connecting said-lastnamedmeans with said throttle bore on the inlet side of said throttle valve,a vacuum chamber, a conduit connecting said chamber with saidsuctionoperated means, a valve in said conduit, a cylinder incommunication with said vacuum chamber, a passage connecting saidcylinder with said throttle bore on the engine side of said throttlevalve, a piston in said cylinder permitting slow leakage of airtherepast in either direction, and means connecting said piston and saidconduit valve whereby movement of said piston in one direction openssaid valve.

5. In a carburetor of the class described, the combination of afuel-feeding nozzle, a-mixing chamber into which said nozzleAdischarges, a throttle bore communicating with said mixing chamber, athrottle valve located in said bore, an air valve for admittingsecondary air to said mixing chamber, a spring for closing said valve,suction-operated means for opening said valve, a restricted conduitconnecting said last-named means with said throttle bore on the inletside of said throttle valve, a vacuum chamber, a conduit connecting saidchamber with said suctionoperated means, a valve in said conduit, acylinder in communication with said vacuum chamber, a passage connectingsaid cylinder with said throttle bore on the engine side of saidthrottle valve, a piston in said cylinder permitting slow leakage of airtherepast in either direction, means connecting said piston and saidconduit valve for conjoint movement, and a springv for urging saidpiston and valve in one direction.

6. In a carburetor, the combination of a-.fuel feeding nozzle, a mixingchamber into which said nozzle discharges, a throttle valve controllingcommunication between said mixing chamber and the manifold of an engineto which said carburetor is connected, an air valve for admitting air tosaid mixing chamber, said valve normally opening in response to mixingchamber suction, suction means independent of mixing chamber suction andresponsive to sudden opening of said throttle valve for opening said airvalve during acceleration, and an accelerator pump operated by saidthrottle valve for supplying said nozzle with an additional quantity offuel.

7. In a carburetor, the combination of a fuel feeding nozzle, a mixingchamber into which said nozzle discharges, a throttle valve controllingcommunication between said mixing chamber and the manifold of an engineto which said carburetor is connected, an air valve for admitting air tosaid mixing chamber, yielding means for closing said air valve, asuction dashpot associated with said air valve for opening said airvalve, said dashpot having a restricted communication with said mixingchamber, a suction cham- Y,

scribed, the combination of a fuel feeding nozzle,-

a mixing chamber into which said nozzle discharges, a fuel chamber forsaid nozzle, a booster for supplying fuel to said fuel chamber, athrottle valve controlling communication between said mixing chamber andthe manifold of an engine to which said carburetor is connected, an airvalve for admitting air to said mixing chamber, said valve normallyopening in' response to mixing chamber suction, an accelerator pump,said accelerator pump being simultaneously operated by said throttlevalve for supplying said nozzle with an additional quantity of fuel, andsuction means independent of mixing chamber suction and responsive tosudden opening of said throttle valve for opening said air valve duringacceleration.

9. In a carburetor of the class described, the combination of a fuelsupply nozzle, a mixing chamber into which said nozzle discharges, asuction actuated valve for admitting secondary air to said chamber, asuction chamber beneath said valve, a spring for closing said valve, athrottle bore communicating with said mixing chamber, means whereby saidvalve is opened an amount proportional to the degree of suction existingin the upper part of said bore, a vacuum chamber, a conduit connectingsaid vacuum chamber with said suction chamber, a valve normally closingsaid conduit, means for opening said last-named valve when thecarburetor is conditioned for rapid engine acceleration, and anaccelerator pump for simultaneously supplying said nozzle with anadditional quantity of fuel.

ROBERT F. BRACKE.

